Bare electronic chips typically need to be assembled in a package that provides an electric circuit to each electrical connection of the chip and to an external connector such as a pin or a ball. Typical is a pin-grid array package having relatively large pins on one side for external connections, and pads on an opposite side for connections to a ball-grid-array set of connections to the electronic chip (such as a processor or memory chip). Also typical is a ball-grid array package having relatively large balls with relatively large spacings on one side of the package for external connections, and small closely spaced pads on the opposite side for connections to a similar ball-grid-array set of connections to the electronic chip (such as a processor or memory chip).
Such a package typically has a non-conductive substrate (such as plastic or ceramic) with conductive traces (wires) on or in a surface of the substrate. Balls and/or pins are attached, and one or more electronic chips are attached, for example, by also using ball-grid-array connection methods. Optionally, a cover or encapsulant is used to enclose the chip or chips. Optionally, a heat-removing device or structure is attached to, or pressed against, the chip or chips.
One conventional way to make such a package is to start with a sheet or strip of dielectric coated with a conductive metal such as copper, then using various drilling, plating, lithographic and metal etching steps form a pattern leaving metal where traces are desired, attach one or more chips to the one side of the remaining pattern, attach pins or balls to the other side, and encapsulate the chip or chips. Such a method is difficult to apply to devices requiring substantial signal routing and/or power-supply capability.
Another conventional way to make such a package is to start with a sheet or strip of non-conductive plastic of ceramic, deposit ink in a pattern that forms the conductive traces, sinter the ink to form metal traces, in order to make a printed-circuit card or printed-wiring substrate. This method is difficult and costly.
What is needed is a simple, inexpensive, reliable method and apparatus to fabricate packages for electronic chips.